linux/kernel/trace/trace_functions_graph.c

/*
 *
 * Function graph tracer.
 * Copyright (c) 2008 Frederic Weisbecker <fweisbec@gmail.com>
 * Mostly borrowed from function tracer which
 * is Copyright (c) Steven Rostedt <srostedt@redhat.com>
 *
 */
#include <linux/debugfs.h>
#include <linux/uaccess.h>
#include <linux/ftrace.h>
#include <linux/fs.h>

#include "trace.h"


#define TRACE_GRAPH_PRINT_OVERRUN	0x1
static struct tracer_opt trace_opts[] = {
	/* Display overruns or not */
	{ TRACER_OPT(overrun, TRACE_GRAPH_PRINT_OVERRUN) },
	{ } /* Empty entry */
};

static struct tracer_flags tracer_flags = {
	.val = 0, /* Don't display overruns by default */
	.opts = trace_opts
};


static int graph_trace_init(struct trace_array *tr)
{
	int cpu;
	for_each_online_cpu(cpu)
		tracing_reset(tr, cpu);

	return register_ftrace_graph(&trace_function_graph);
}

static void graph_trace_reset(struct trace_array *tr)
{
		unregister_ftrace_graph();
}


enum print_line_t
print_graph_function(struct trace_iterator *iter)
{
	struct trace_seq *s = &iter->seq;
	struct trace_entry *entry = iter->ent;
	struct ftrace_graph_entry *field;
	int ret;

	if (entry->type == TRACE_FN_RET) {
		trace_assign_type(field, entry);
		ret = trace_seq_printf(s, "%pF -> ", (void *)field->parent_ip);
		if (!ret)
			return TRACE_TYPE_PARTIAL_LINE;

		ret = seq_print_ip_sym(s, field->ip,
					trace_flags & TRACE_ITER_SYM_MASK);
		if (!ret)
			return TRACE_TYPE_PARTIAL_LINE;

		ret = trace_seq_printf(s, " (%llu ns)",
					field->rettime - field->calltime);
		if (!ret)
			return TRACE_TYPE_PARTIAL_LINE;

		if (tracer_flags.val & TRACE_GRAPH_PRINT_OVERRUN) {
			ret = trace_seq_printf(s, " (Overruns: %lu)",
						field->overrun);
			if (!ret)
				return TRACE_TYPE_PARTIAL_LINE;
		}

		ret = trace_seq_printf(s, "\n");
		if (!ret)
			return TRACE_TYPE_PARTIAL_LINE;

		return TRACE_TYPE_HANDLED;
	}
	return TRACE_TYPE_UNHANDLED;
}

static struct tracer graph_trace __read_mostly = {
	.name	     = "function-graph",
	.init	     = graph_trace_init,
	.reset	     = graph_trace_reset,
	.print_line = print_graph_function,
	.flags		= &tracer_flags,
};

static __init int init_graph_trace(void)
{
	return register_tracer(&graph_trace);
}

device_initcall(init_graph_trace);